Magnetic transfer method and magnetic transfer device

ABSTRACT

A magnetic transfer method which superposes on a magnetic disk surface a magnetic pattern from a master disk ( 2 ), said master disc having on its surface a magnetic film formed so as to have an array pattern shape corresponding to a preset data signal, magnetized into the magnetic film of the master disk ( 2 ). The master disc is used to magnetically transfer the array pattern of the data signal onto the magnetic disk as the magnetized pattern of the data signal. The method characterized comprises steps of contacting and separating, to and from a dummy disk ( 1 ) the magnetic film-formed surface of the master disk ( 2 ) to thereby clean the master disk ( 2 ), and a step of superposing, after the cleaning, the master disk ( 2 ) on the magnetic disk for effectuating the magnetic transfer.

This application is a U.S. national phase application of PCTInternational application PCT/JP00/02679.

FIELD OF THE INVENTION

The present invention relates to a method of magnetic transfer and anapparatus for magnetic transfer for magnetic transferring in a processof manufacturing magnetic discs used for hard disc devices and floppydisc devices.

As a typical magnetic disc device, there have already beencommercialized presently some of hard disc drives having a surfacerecording density exceeding 1 Gigabit/sq-in, and rapid technologicaladvancement is strongly in evidence as there are discussions aboutpractical use of 20 Gigabit/sq-in within a few years.

In the technological background, what has enabled such a high recordingdensity is dependent largely upon magneto-resistive element heads thatare capable of reproducing signals in only a few μm of track width witha high signal-to-noise ratio, besides improvements in the trackrecording density.

In addition, there have been demands for reduction in amount of flotageof a floating magnetic slider with respect to a magnetic recordingmedium in keeping with high recording density, as there are increasing apossibility of physical interactions that can occur between the disc andthe slider for certain factors even while floating. Under suchcircumstances, there has been a demand for further smoothness of therecording media.

Here, tracking servo techniques of the head play an important role inorder for the head to accurately scan a narrow track. In a currentlyavailable hard disc drive using such tracking servo techniques, a servosignal for tracking, an address data signal, a reproduction clock signaland the like are recorded at regular angular intervals in a round of thedisc. A driving device detects and corrects a position of the head usingthese signals reproduced by the head at predetermined time intervals,thereby enabling the head to scan over the track accurately.

Since the above-described servo signal, the address data signal, thereproduction clock signal and the like are used as reference signals forthe head to scan accurately over the track, a high positioning accuracyis required for writing them (hereinafter referred to as “formatting”).In the current hard disc drives, formatting is made with aspecial-purpose servo device (henceforth “servo writer”) equippedtherein with a highly accurate position detecting device, which utilizesoptical interference to position the recording head.

However, the following problems exist in the formatting made by theservo writer.

First, it takes a considerable time to write signals over a large numberof tracks while positioning the head with a high accuracy. It istherefore necessary to operate many servo writers at the same time inorder to increase productivity.

Secondly, it costs a large amount of money to provide a large number ofthe servo writers and to maintain them. These problems become moreserious the more the number of tracks increases as a track densityimproves.

Hence, there has been proposed a method in that a disc called masterdisc, on which a complete servo data is written in advance, isoverlapped with a magnetic disc to be formatted, and the data on themaster disc is transferred into the magnetic disc in batch by externallyimpressing energy for the magnetic transfer, thus formatting isperformed instead of using a servo writer.

A magnetic transfer apparatus described in Japanese Patent Laid-OpenPublication, No. H10-40544, is now cited as an example.

The above publication discloses a method including the steps of forminga magnetic area composed of ferromagnetic material in a shape of apattern corresponding to data signals on a surface of a substrate toprepare a master disc for magnetic transfer, making the surface of themaster disc for magnetic transfer to be in contact with a surface of amagnetic recording medium of either a sheet-form or a disc-form whereoneither a ferromagnetic thin film or a coated layer of ferromagneticpowder is formed, and recording on a magnetic recording medium amagnetized pattern in a shape of the pattern corresponding to the datasignals formed on the master disc for magnetic transfer by applying amagnetic field of a predetermined magnitude.

However, since there is normally a clearance of approximately 30 nmbetween the head and a surface of the disc when the disc is in rotation,it is therefore necessary to keep unevenness on the surface of the discwithin a maximum of approximately 20 nm. The magnetic head may come incontact with the magnetic recording medium during recording andreproducing the data, if any bumps larger than the above exist on themagnetic recording medium. In such a case, a space between the magnetichead and the magnetic disc increases at the instant of contact, andcauses performance of recording and reproducing signals to decrease. Ithas also been a cause of shortening a useful life of the magnetic head,as the magnetic head makes physical contact with the magnetic disc.

In other words, although the magnetic transfer apparatus disclosed inJapanese Patent Laid-Open Publication, No. H10-40544, can complete theformatting instantly, it requires a strict surface control, on the otherhand, in order to ensure practical use with the foregoing clearancebetween the head and the disc, since the master disc for magnetictransfer and the magnetic disc come in contact over the entire surfaces.

In addition, disc-shaped recording media such as magnetic discs,magneto-optical discs, optical discs and the like are advancing towardhigher performance such as downsizing, thinning, increased capacity andso on in recent years, and demands for higher density recording mediahave been rising in keeping pace with the advancement as describedabove. Disc-shaped recording media having high accuracy and highreliability are necessary in order to meet such demands, thereforemaking it an urgent need to manufacture disc-shaped recording media withoutstanding flatness and smoothness, and without adhesion of fineparticle, etc. during recording of data.

On the contrary, it is difficult for the above-described magnetictransfer apparatus of the prior art to avoid fine foreign particles fromgetting into it, even if very strict control is carried out. Suchforeign particles have caused small anomalous unevenness on a surface ofthe master disc or the magnetic disc at a moment the master disc and themagnetic disc to be formatted are overlapped together. Silicon is usedgenerally as material of the master disc. If the magnetic disc is madeof a material of lower hardness than that, such as aluminum for example,bumps of foreign particles on the master disc are transferred in shapeas dimples on the magnetic disc side, and if on the other hand themagnetic disc is made of a material of higher hardness such as glass forexample, foreign particles located on the magnetic disc produce defectson the master disc side.

In the above case, the defects are reproduced on all of magnetic discsto which magnetic transfer is performed, thereby making it difficult tomanufacture the magnetic discs of high quality efficiently and steadily.

Accordingly, the present invention is intended to realize a magnetictransfer apparatus that is capable of accurate magnetic transfer inorder to manufacture magnetic discs of high quality by decreasing sizeof such small bumps to a level not to cause the problems, and to preventerrors in recording and reproducing.

SUMMARY OF THE INVENTION

A method of magnetic transfer of the present invention is amanufacturing method including the steps of closely contacting a masterdisc for magnetic transfer, whereon a magnetic film is formed, with asurface of a magnetic disc, whereon a ferromagnetic layer is formed, andmagnetically transferring a pattern of the magnetic film on the masterdisc for magnetic transfer onto the surface of the magnetic disc usingan external magnetic field, wherein the magnetic transfer is carried outby mounting the regular magnetic disc only after repeating suctioningand forced feeding of gas between the master disc for magnetic transferand a dummy disc, when making the master disc for magnetic transfer tocontact forcibly by using the dummy disc first. Taking this method canmaintain a surface of the master disc for magnetic transfer in a smoothcondition free from foreign particles and burrs at all the time duringmagnetic transferring, thereby realizing manufacture of magnetic discsof high quality, as there occurs practically no fine bump to causeproblems, as far as the magnetic discs subject to the magnetic transferare concerned.

Also, the method of magnetic transfer of the present invention furtherincludes defect detection means for detecting defects on a surface of amagnetic disc. When this defect detection means detects defects innumber equal to or greater than a predetermined number on the surface ofthe magnetic disc, the magnetic transferring is carried out by placingit in close contact with a master disc for magnetic transfer, only afterrepeating an operation of contacting and separating the master disc formagnetic transfer with a dummy disc for a predetermined number of times,and replacing the dummy disc by the magnetic disc not subjected to themagnetic transfer. The above step helps to provide the method ofmagnetic transfer capable of ensuring the magnetic transferring of highquality into magnetic discs for a long period of time, since it allows aregular maintenance of removing dust and foreign particles on the masterdisc for magnetic transfer.

Furthermore, in the present invention, a region on the master disc formagnetic transfer where contacting with and separating from the dummydisc is so arranged as to completely cover a magnetic transfer regionfrom the master disc for magnetic transfer to the magnetic disc duringmagnetic transfer. This realizes manufacture of magnetic discs of highquality, as servo signals are accurately transferred even on a rim in aperipheral area of the magnetic disc.

Moreover, the method of magnetic transfer of the present invention is tocarry out the magnetic transfer by placing the master disc for magnetictransfer in close contact with a magnetic disc, only after repeating anoperation of contacting and separating a dummy master disc with themagnetic disc for a predetermined number of times, and replacing thedummy master disc by the master disc for magnetic transfer. This methodis able to remove foreign particles on the magnetic disc, therebyrealizing an accurate magnetic transfer while assuring a remarkablysmooth surface and high reliability.

Furthermore, an apparatus for magnetic transfer of the present inventionis to make a master disc for magnetic transfer, whereon a magnetic filmis formed on at least one of surfaces thereof, in close contact with amagnetic disc, and to magnetically transfer a pattern of the magneticfilm on the master disc for magnetic transfer onto the magnetic disc byapplying an external magnetic field. The apparatus for magnetic transferincludes the master disc for magnetic transfer whereon a predetermineddata to be transferred is written, a retainer slidably positioned on aguide member for retaining the master disc for magnetic transfer, asupport base provided with a vent hole for supporting the magnetic discor a dummy disc, a feeding unit for supplying gas into the vent holeprovided in the support base, an exhaust unit for evacuating gas throughthe vent hole, and a magnet for applying magnetic field for the magnetictransfer. The foregoing structure is able to maintain a surface of themaster disc for magnetic transfer in a smooth condition free fromforeign particles and burrs at all the time during magnetictransferring, thereby realizing manufacture of magnetic discs of highquality as practically no small bump occurs on the magnetic discssubject to the magnetic transfer.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flow chart showing a process in a first exemplary embodimentof the present invention;

FIG. 2 is a sectional view of a magnetic transfer apparatus of the firstexemplary embodiment of the invention;

FIG. 3 is a sectional view of the magnetic transfer apparatus depictinga state wherein a master disc for magnetic transfer and a dummy disc areclosely in contact with each other in the magnetic transfer apparatus ofFIG. 2;

FIG. 4 is an illustration depicting a surface of the master disc formagnetic transfer to be in contact with the magnetic disc in the firstexemplary embodiment of the invention;

FIG. 5 is an illustration depicting an example of a shape of a boss onthe master disc for magnetic transfer in the first exemplary embodimentof the invention;

FIG. 6 is a graphical representation showing a change in gas pressurewith lapse of time in a space S by suctioning and forced feeding of thegas in the magnetic transfer apparatus of the first exemplary embodimentof the invention;

FIG. 7 is a perspective view of a magnetic disc depicting a statewherein it is magnetized in one direction;

FIG. 8 is another view of the magnetic disc depicting a state whereindata signals corresponding to a shape of pattern of a magnetic part of amaster disc is recorded in a predetermined area thereof;

FIG. 9 is a drawing showing a process of magnetic transferring datasignals corresponding to a shape of pattern formed on a master disc ontoa magnetic disc;

FIG. 10 is a graphical representation showing a data taken by a foreignobject measuring apparatus on a surface of a magnetic disc whereonmagnetic transfer is performed with the magnetic transfer apparatus ofthe first exemplary embodiment of the invention;

FIG. 11 is a graphical representation showing a data taken by theforeign object measuring apparatus on a surface of a magnetic discwhereon magnetic transfer is performed with a magnetic transferapparatus of the prior art;

FIG. 12 is a graphical representation showing a relation between numberof defects on a surface of a magnetic disc and number of repeated cyclesof suctioning and pressurized feeding;

FIG. 13A is an illustration showing burrs produced in an initial stagein a edge portion of a track pattern formed on a master disc formagnetic transfer;

FIG. 13B is another illustration showing burrs produced in a stage aftersuctioning and forced feeding are repeated;

FIG. 13C is an illustration showing a bump formed in the initial stageon the master disc for magnetic transfer;

FIG. 13D is another illustration showing a bump formed in the stageafter the suctioning and forced feeding are repeated;

FIG. 14 is a schematic illustration showing an example of a signal areaon a master disc for magnetic transfer in the first exemplary embodimentof the invention;

FIG. 15 is an enlarged schematic illustration showing a portion of thesignal area on a master disc for magnetic transfer in the firstexemplary embodiment of the invention;

FIG. 16 is a sectional schematic illustration showing a portion of thesignal area of a master disc for magnetic transfer in the firstexemplary embodiment of the invention;

FIG. 17 is a flow chart showing a process in a magnetic transfer methodof a second exemplary embodiment of the present invention;

FIG. 18 is a graphical representation showing relations between numberof foreign particles and defects on a surface of a master disc formagnetic transfer and number of suctioning/forced feeding in case ofwith and without lubricant on a dummy disc;

FIG. 19A is an illustration depicting a reproduced signal envelope of asignal recorded on a magnetic disc after magnetic transfer is performedby using a dummy disc coated with lubricant;

FIG. 19B is another illustration depicting a reproduced signal envelopeof a signal recorded on a magnetic disc after magnetic transfer isperformed by using a dummy disc not coated with lubricant;

FIG. 20A is an illustration schematically depicting a relation between amaster disc for magnetic transfer and a dummy disc during suctioning andforced feeding in a third exemplary embodiment of the present invention,wherein the former is made larger in size than the latter;

FIG. 20B is another illustration schematically depicting a relationbetween the master disc for magnetic transfer and a magnetic disc duringthe suctioning and forced feeding, when positioning of the latter isshifted from where the dummy disc had been installed, in the thirdexemplary embodiment of this invention;

FIG. 21 is an illustration showing an example of positions on the masterdisc for magnetic transfer of a larger size whereto the dummy disc isclosely contacted in the third exemplary embodiment of this invention;

FIG. 22 is a flow chart showing a process in a magnetic transferapparatus of a fourth exemplary embodiment of the present invention;

FIG. 23 is a graphical representation showing a surface of a master discfor magnetic transfer in a state after a process of suctioning andpressurized feeding is made in the fourth exemplary embodiment of thisinvention; and

FIG. 24 is another graphical representation showing a surface of themaster disc for magnetic transfer in a state when the process ofsuctioning and pressurized feeding in the fourth exemplary embodiment ofthis invention is not made.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Exemplary embodiments of the present invention are described hereinafterby referring to accompanying figures.

The present invention relates to a method of magnetic transfer and anapparatus for magnetic transfer, wherein magnetic transferring is madeby overlapping a master disc for magnetic transfer onto a magnetic discafter the master disc for magnetic transfer is cleaned by closelycontacting a surface of the master disc for magnetic transfer, on whichsurface a magnetic film is formed, with a dummy disc.

In each of the following exemplary embodiments of the invention, whatare described pertain to the method of magnetic transfer formagnetically transferring a pattern of magnetic film of the master discfor magnetic transfer onto a surface of a regular magnetic disc, and theapparatus for magnetic transferring.

First Exemplary Embodiments

A method of magnetic transfer and an apparatus for magnetic transfer ofa first exemplary embodiment of the present invention will now bedescribed by referring to FIG. 1 through FIG. 6.

FIG. 1 is a flow chart showing the method of magnetic transfer of thisexemplary embodiment. In FIG. 1, at first a ferromagnetic thin filmcomposed of cobalt, for instance, or the like is formed as a magneticlayer on a surface of a regular magnetic disc (hereinafter referred toas “magnetic disc”) by a known method such as the sputtering method.

On the other hand, a dummy disc is installed in the magnetictransferring apparatus (hereinafter, “apparatus”). Suctioning and forcedfeeding of gas between both discs are repeated after a master disc formagnetic transfer (hereinafter, “master disc”) is brought close to adummy disc, and magnetic transfer is carried out after the dummy disc isreplaced with the magnetic disc. Here it is premised that the masterdisc is installed in the apparatus in advance.

Next, a process shown in FIG. 1 for magnetic transfer will be describedin detail by using FIG. 2 to FIG. 5.

FIG. 2 is a sectional view of the magnetic transfer apparatus of thisexemplary embodiment, showing a state wherein the master disc 2 and thedummy disc 1 are separated with respect to each other. FIG. 3 showsanother state when the master disc 2 and the dummy disc 1 are in closecontact with each other. FIG. 4 is an illustration depicting a contactsurface 3 of the master disc 2, with which the magnetic disc contacts,and grooves 4 extend radially from the center of the master disc 2. Adepth of the grooves is set for approximately 5 μm in this exemplaryembodiment.

In FIG. 2, the dummy disc 1 is replaced with a magnetic disc after aprocess of suctioning and forced feeding of gas. Aluminum is used asmaterial of the dummy disc. Silicon is used as material of the masterdisc 2, as it is desirable because silicon has higher hardness thanaluminum. The grooves 4 (refer to FIG. 4) extending radially from thecenter of the master disc 2 are provided in the contact surface 3 to bein contact with the dummy disc 1 on the master disc 2. The master disc 2illustrated in FIG. 2 represents a surface that is sectioned along abreak line 2—2 drawn through the grooves as shown in FIG. 4.

A boss 5 is attached to the center portion of the master disc 2, and itengages in an inner peripheral hole of the dummy disc 1 with a gap. Asupport base 6 supports the dummy disc 1, and it has a vent hole 7 in acenter for flowing air. A passage 8 is for exhausting and forcefullyfeeding gas between the master disc 2 and the dummy disc 1. The gas isexhausted by a suction pump 10 connected with a gas outlet 9, afterpassing through the gas outlet 9 and an exhaust valve 11 which controlsexhaust of the gas. Further, a feed pump 12 feeds the gas forcefully tothe passage 8 through a feed valve 13, and the feed valve 13 controls asupply of the gas. In this embodiment, the feed pump 12 is provided withan air filter of 0.01 μm, thereby avoiding foreign particles larger than0.01 μm from being fed forcefully into the passage 8.

A retaining arm 14 for retaining the master disc 2 holds the master disc2. Although there are a number of retaining methods including bondingand so on, the master disc 2 may be vacuum-chucked by suctioning gasfrom a through hole 19 provided in the retaining arm 14, as shown inFIG. 2.

The retaining arm 14 is then positioned in a slidable manner in avertical direction via an extended portion on an upper part thereof by aguide member 16.

However, the method of positioning the master disc 2 is not limited tothe one using the retaining arm 14, but it can also be achieved, forinstance, by fitting an outer periphery of the boss 5 in an innerperipheral hole of the magnetic disc (it is the dummy disc 1 in thisprocess). If this is the case, the boss 5 may be made in a shape asshown in FIG. 5, and the gas between the master disc 2 and the dummydisc 1 is evacuated and force-fed through cut openings 51 providedaround periphery of the boss 5.

Next, a process of suctioning and forced feeding will be described indetail by using FIGS. 2 to 4.

Referring to FIG. 2, a process of separation using forced feeding willbe described first. The gas is supplied into the passage 8 by operatingthe feed pump 12 while the exhaust valve 11 is closed and the feed valve13 opened. This causes air to be fed forcefully into the vent hole 7 inan upward direction as show by an arrow A in FIG. 2. This makes the airfed forcefully into the vent hole 7 to push up the boss 5 upwardly, andthe air is fed forcefully further into the grooves 4 as shown by arrowsB. The air fed forcefully into the grooves 4 spreads radially from acenter toward an outer periphery of the master disc 2 through thegrooves 4. And the air gets out into the atmosphere from the grooves 4by passing further through spaces between the master disc 2 and thedummy disc 1. This flow of the air expels fine foreign particlesadhering to the surfaces of the master disc 2 and the dummy disc 1 tothe outside together with the gas.

FIG. 6 shows a relation between lapse of time and gas pressure withinthe space (hereinafter referred to as “space S”) confined between themaster disc 2 and the dummy disc 1 when the process is shifted from asuctioning step to a forced feeding step. In FIG. 6, the gas pressure inthe space S shoots up rapidly from 30 kPa at about 3 seconds in thelapse of time, and a period of approximately 1 second thereafter, inwhich the gas pressure of about 130 kPa, higher than the atmosphericpressure, is maintained, corresponds to the state shown in FIG. 2wherein the master disc 2 and the dummy disc 1 are separated.

It is desirable, in this state, that the space between the master disc 2and the dummy disc 1 is set to be as small as possible. It is set toapproximately 0.5 mm in the present exemplary embodiment. Accordingly,fine foreign particles that exist between the master disc 2 and thedummy disc 1 can be expelled reliably to the outside, since flow of thegas between the two is accelerated.

In this exemplary embodiment, a distance between the dummy disc 1 andthe master disc 2 is controlled by setting an upper surface of theretaining arm 14 to come in contact with a lower surface of the guidemember 16 when the master disc 2, together with the retaining arm 14,rises by 0.5 mm from a position where the master disc 2 is closely incontact with the dummy disc 1.

A process of making a close contact by suctioning will be described nextby referring to FIG. 3.

The feed pump 12 is stopped, and the feed valve 13 is shut. This allowsthe retaining arm 14 holding the master disc 2 to move downwardly by itsown weight, and the master disc 2 is disposed on the dummy disc 1 whilethe boss 5 stays in its engaged position with the inner peripheral holeof the dummy disc 1. Afterwards, the exhaust valve 11 is opened, and thesuction pump 10 is operated. This exhausts the gas in the grooves 4,i.e. the space S, through the gap between the inner peripheral hole ofthe dummy disc 1 and the boss 5, since the gas in the vent hole 7 isexhausted downwardly as shown by an arrow C in FIG. 3.

During this process, the space S is in a state of being sealed airtight,and the pressure is lower than the atmospheric pressure, since themaster disc 2 and the dummy disc 1 are in a position of closely incontact with each other over their entire perimeters at their outermostperipheral portions having heavy thickness because the grooves 4 are insuch a shape as not to extend through the outer perimeter of the masterdisc 2, as shown in FIG. 4. The dummy disc 1 is therefore pressedagainst the master disc 2 by the atmospheric pressure 15 (FIG. 3).

As a result, foreign particles in existence on the dummy disc 1, arecaught between the dummy disc 1 and the master disc 2. At this moment,the foreign particles caught between the dummy disc 1 and the masterdisc 2 lodge in or produce defects on the surface of the dummy disc 1without damaging the surface of the master disc 2, since hardness of thedummy disc 1 is lower when the dummy disc 1 and the master disc 2 arecompared of their hardness. In addition, small anomalous bumps presenton the surface of the master disc 2 are made smoother by coming in closecontact with the dummy disc 1.

A period in which the gas pressure in the space S is about 30 kPa inFIG. 6 corresponds to the foregoing state of close contact.

However, shape of the grooves 4 needs not be limited to the onedescribed above. A member adaptable to sealing the perimeter of themaster disc 2 and the dummy disc 1 may be disposed, if the grooves 4have a shape extending through the perimeter of the master disc 2.

Next, the process of separation shown in FIG. 2 is carried out again.That is, the exhaust valve 11 is closed, the feed valve 13 is opened,and the feed pump 12 is operated. The gas is then fed forcefully asshown by the arrows A and B, the master disc 2 moves together with theretaining arm 14 by the force of the forced-fed gas, and it stops in theposition where the upper surface of the retaining arm 14 comes incontact to the guide member 16. At this moment, the gas remains in thestate of being fed forcefully from the center through the grooves 4radially toward the outer perimeter of the master disc 2. This expelsthe foreign particles present on the surface of the dummy disc 1 to theoutside together with the gas fed forcefully from the feed pump 12.

After the aforementioned suctioning and forced-feeding are repeated fora redetermined number of times, the dummy disc 1 is replaced with aregular magnetic disc 100, the aforementioned process of suction isexecuted for the magnetic disc 100, and a process of imposing magneticfield is carried out while the magnetic disc 100 is in a position ofclose contact with the master disc 2 as shown in FIG. 3.

In other words, a magnet 17 is moved in a direction of an arrow D asshown in FIG. 3 to a close vicinity of the master disc 2, and themovement toward the direction of arrow D is stopped when a distance toit becomes approximately 1 mm. Next, magnetic field in a magnituderequired for the transcription is applied by rotating the magnet 17 byone complete rotation or more in a direction of a circumference of themagnetic disc 100, i.e. a direction of an arrow E.

At this time, a procedure for transferring and recording the datasignals corresponding to the shape of pattern formed on the master disc2 into the magnetic disc 100 will be described in more detail byreferring to FIGS. 7 to 9.

First of all, the magnet 17 is rotated in parallel with the master disc2 around the center axis of the master disc 2 as its rotary axis, withthe magnet 17 brought in the position close to the master disc 2. Thispreliminarily magnetizes the magnetic disc 100 in one direction as shownby arrows in FIG. 7 (initial magnetization).

Then, the magnet 17 is rotated in a direction opposite to the arrow E inFIG. 3 after the master disc 2 and the magnetic disc 100 are made tocontact evenly with the master disc 2 set in position and overlapped onthe magnetic disc 100 as described above. In other words, an applicationof the magnetic field in the direction opposite to the initialmagnetization magnetizes magnetic parts 26 on the master disc 2. It thenrecords the data signals, which correspond to the shape of pattern ofthe magnetic parts 26 of the master disc 2, on predetermined areas 116,which also correspond to the magnetic parts 26 of the master disc 2, ofthe magnetic disc 100 overlapped with the master disc 2, as shown inFIG. 8. Arrows shown in FIG. 8 indicate a direction of the magneticfield of a magnetized pattern transferred and recorded into the magneticdisc 100 during this process.

FIG. 9 shows what is taking place in the process of magnetization,wherein the data signals can be recorded in a ferromagnetic layer 1 c ofthe magnetic disc 100 by magnetizing the magnetic parts 26 with anapplication of the magnetic field from the outside to the master disc 2while the master disc 2 is placed in close contact with the magneticdisc 100. That is, transferring and recording can be made magneticallyinto the magnetic disc 100 as a magnetized pattern corresponding to thedata signals by using the master disc 2 composed of a nonmagneticsilicon substrate 2 b and the magnetic parts 26 of ferromagnetic thinfilm formed thereon in the shape of a pattern arranged to correspondwith predetermined data signals.

There are other methods of transferring and recording the pattern of themaster disc 2 into the magnetic disc 100, besides the method of applyingthe external magnetic field to the master disc 2 positioned in contactwith the magnetic disc 100 as described above. That is, the data signalscan be recorded even with a method in which magnetic parts 26 of amaster disc 2 is magnetized beforehand and this master disc 2 is made tocontact closely together with a magnetic disc 100.

Condition of surfaces of the magnetic discs completed here, representedby a result of measurements taken by a particle measuring apparatus areshown in FIG. 10 and FIG. 11. FIG. 11 shows a condition of a magneticdisc surface on which transfer was made with the conventionaltransferring method, that is, no dummy disc was used for the abovedescribed operation of suctioning and forced feeding. Table 2 shows arelation between depth of defects and number of the defects produced bythe conventional transferring method.

TABLE 1 Depth of defects 40 nm or deeper 50 nm or deeper 60 nm or deeperNumber 2 0 0 of defects

TABLE 2 Depth of defects 40 nm or deeper 50 nm or deeper 60 nm or deeperNumber 24 18 7 of defects

It is known from FIG. 11 and Table 2 that there are 24 defects having 40nm or greater in depth in existence in the surface of the magnetic disc,and many of them in a peripheral area.

On the other hand, FIG. 10 represents a graphical figure showing acondition of a magnetic disc surface on which magnetic transfer was madewith this regular magnetic disc 100 replaced after the above describedoperation of suctioning and forced feeding was made 100,000 times usinga dummy disc. Table 1 shows a relation between depth of defects andnumber of the defects in this case. It is known from Table 1 that thereare 2 defects having depth equal to or greater than 40 nm in existencein the surface of the magnetic disc.

It is obvious from these figures that defects previously existed in themagnetic disc due to the anomalous bumps on the master disc 2 decreasesubstantially because the surface of the master disc 2 is smoothed byrepeating the operation of suctioning and forced feeding using the dummydisc.

Here, a relation between number of suctioning and forced feedingoperations and number of defects in depth of 40 nm or greater isgraphically represented in FIG. 12. It is known from FIG. 12 that thenumber of defects decreases as the number of suctioning and forcedfeeding operations is increased.

In addition, FIGS. 13A through 13D show conditions of surfaces of themaster disc 2 at an initial stage and after the suctioning andforce-feeding is repeated.

It is obvious that burrs 22 produced in the initial stage in a edgeportion of a track pattern 21 formed on the master disc 2, as shown inFIG. 13A, are smoothed as shown in FIG. 13B after the 100,000 cycles ofsuctioning and forced feeding.

It is also obvious that a bump 23 existed initially as shown in FIG. 13Cis smoothed, and it has almost disappeared except for a tip 24 of thebump, of which a magnitude of projection was highest, as shown in FIG.13D, after the 100,000 cycles of suctioning and forced feeding.

As has been described, the present exemplary embodiment makes itpossible to manufacture magnetic discs of high quality having extremelysmooth surfaces, and realizes accurate magnetic transfer, since itremoves foreign particles that exist on the surface of the master disc 2and smoothes anomalous bumps by executing the operation of suctioningand forced feeding using the dummy disc before the process of magnetictransfer.

With regard to the dummy disc, it is necessary to replace with a newdummy disc if stain or a number of foreign particles on the surfaceexceed predetermined levels.

Further, it is desirable that hardness of the surface of the dummy discis lower than that of the surface of the master disc as stated in thepresent exemplary embodiment. This is because no dimple is produced onthe surface of the dummy disc, if there is a foreign particle higher inhardness than that of the surface of the master disc but lower than thatof the dummy disc in existence between the master disc 2 and the dummydisc 1, since the hardness of the surface of the dummy disc is higherthan that of the foreign particle, when the hardness of the surface ofthe dummy disc is higher than that of the surface of the master disc. Inother words, the foreign particle does not stick to the surface of thedummy disc. Therefore, the foreign particle stays stuck on the surfaceof the master disc. This can be a cause of a defect, as the foreignparticle produces a dimple in a surface of the master disc, when thedummy disc 1 and the master disc 2 get in close contact with each otherafterward, since the hardness of the foreign particle is higher thanthat of the surface of the master disc.

Contrary to the above, it is possible to securely avoid dimples frombeing produced in the master disc, at a time of close contact of thedummy disc 1 and the master disc 2, by decreasing the hardness of thesurface of the dummy disc to be lower than that of the surface of themaster disc, for the reason as described above.

Furthermore, although aluminum is selected as material of the dummy discin the present exemplary embodiment, this is not restrictive. A discmade of aluminum with a plated layer formed thereon may be used as adummy disc. It is preferable to use a material having ferromagneticproperty such as Co—Re—P, Co—Ni—P, and Co—Ni—Re—P for the plated layer.Formation of the plated layer having a magnetic property on the surfaceof the dummy disc provides the following effect. That is, although themagnetic film on the master disc 2 peels off the master disc 2 by therepeated operation of close contact and separation between the masterdisc 2 and the dummy disc 1 if an anomalous bump exists on the magneticfilm covering the surface of the master disc 2, a peeled piece of themagnetic film sticks to the dummy disc side, since the plated layerhaving magnetic property is formed on the surface of the dummy disc 1.

Moreover, although a varnishing process is not executed in the presentexemplary embodiment, the varnishing process may be added using a tape,a head, buffing abrasives, and the like, for instance, and polishingpowder or grinding powder left on a surface of the magnetic disc afterthe varnishing process can be removed thereafter by carrying out theprocess of suctioning and forced feeding described above. In this case,the pressure of suctioning may be set relatively higher to about 60 kPa,for instance, while the pressure for forced feeding is left unchanged inFIG. 6, in order to improve an effect of the removal.

The master disc 2 shown in FIG. 4 is described in detail at this time.

FIG. 14 schematically illustrates a surface of an example of the masterdisc 2 for magnetic transfer. As shown in FIG. 14, there is a signalarea 2 a formed generally radially on one of main surfaces of the masterdisc 2, i.e. the contact surface 3 at a side which gets in contact witha surface of the ferromagnetic thin film on the magnetic disc 100. AsFIG. 4 and FIG. 14 are schematic illustrations, the signal area 2 a inFIG. 14 is composed actually on the contact surface 3 excluding thegrooves 4 in FIG. 4.

An enlarged view of a portion A circled with a dotted line in FIG. 14 isshown schematically in FIG. 15. As shown in FIG. 15, there are formeddigital data signals to be recorded on magnetic disc in the signal area2 a. For instance, a master disc data pattern in a shape of patterncorresponding to the data signals described above is formed withmagnetic parts composed of ferromagnetic thin film in a positioncorresponding to pre-format recording. In FIG. 15, portions withhatching are the magnetic parts composed of a ferromagnetic thin film.The master disc data pattern shown in FIG. 15 includes areas for each ofclock signal 31, tracking servo signal 32, address data signal 33, andso on arranged one after another in a direction of a track length withrespect to a track length direction 34 of the disc. Data signal areas 35are also shown. The master disc data pattern shown in FIG. 15 is one ofexamples, and a construction, an arrangement, and the like of the masterdisc data pattern are determined appropriately according to digital datasignals to be recorded in the magnetic recording media.

In the case of a hard disc drive, wherein reference signals are firstrecorded on a magnetic film of a hard disc, and pre-format recording oftracking servo signals, etc. is made thereafter according to thereference signals, for instance, only the reference signals for thepre-format recording are transferred in advance on the magnetic film ofthe hard disc using the master disc of this invention, and the hard discis built into an enclosure of the drive, so that pre-format recording ofthe tracking servo signals, etc. may be made using a magnetic head inthe hard disc drive.

A sectional view of a part of the area shown in FIG. 14 and FIG. 15 isdepicted in FIG. 16.

As shown in FIG. 16, the master disc 2 includes a disc-like substrate 41composed of nonmagnetic material such as a silicon substrate, a glasssubstrate, a plastic substrate, and the like, of which one of mainsurfaces, i.e. a contact surface 3 at a side whereto a surface of themagnetic disc 100 comes in contact, is formed with recesses 42 in ashape of a plurality of fine layout pattern corresponding to the datasignals, and ferromagnetic thin films 43, each defining the magneticpart, inlaid in the recesses 42 of the substrate 41.

Many kinds of magnetic material can be used as the ferromagnetic thinfilm 43 for example hard magnetic material, semi-hard magnetic materialor soft magnetic material. Any material is adoptable so long as it cantransfer and record digital data signals into a magnetic recordingmedium. Iron, cobalt, iron-cobalt alloy and so on, for instance, can beused. The larger the saturation magnetic flux density of the magneticmaterial, the better for generating an enough level of recordingmagnetic field without depending on kind of the magnetic recordingmedium in which master disc data is recorded. In particular, there areoccasionally cases in that a satisfactory recording can not be made intoa magnetic disc of a high coercive force exceeding 2000 Oersteds and aflexible disc having a magnetic layer of large thickness, if thesaturation magnetic flux density becomes 0.8 Tesla or less. In general,magnetic materials having a saturation magnetic flux density of 0.8Tesla or greater, and preferably 1.0 Tesla or greater, are used.

In addition, a thickness of the ferromagnetic thin film 43 depends on abit length, saturation magnetization of the magnetic recording mediumand a film thickness of the magnetic layer. But, the thickness of 50 nmto 500 nm may be appropriate in the case of, for instance, approximately1 μm in bit length, approximately 500 emu/cc in saturation magnetizationof the magnetic recording medium, and approximately 20 nm in thicknessof the magnetic layer of the magnetic recording medium.

In a method of recording such as the above, it is desirable to make auniform magnetization, based on a shape of their layout pattern of asoft magnetic thin film or a semi-hard magnetic thin film as theferromagnetic thin film provided on the master disc, by exciting themduring a pre-format recording in order to obtain recording signals ofexcellent quality. It is also preferable to uniformly DC erase themagnetic recording medium such as a hard disc prior to recording thesignals using the master disc.

Next, a method of manufacturing the master disc will be described.

The master disc for use in a recording method of the present inventionis prepared by a method including the steps of: forming a resist film ona surface of a silicon substrate; patterning the resist film by exposingand developing it with the lithography technique using laser beam orelectron beam such as used in the photolithographic method; followed byforming fine recesses and ridges corresponding to data signals byetching it with dry etching, etc.; then forming a ferromagnetic thinfilm including cobalt or the like thereafter by sputtering, vacuumdeposition, ion plating, CVD, plating, and the like method; and removingthe resist film by a so-called lift-off method. This produces the masterdisc provided with magnetic parts corresponding to the data signal in aform of ferromagnetic thin film inlaid in the recesses.

Method of forming the recesses and ridges on the surface of the masterdisc is not limited to the method described above. The fine recesses andridges can be formed directly on it using laser, electron beam, ionbeam, or by machining.

What has been described in this exemplary embodiment is an example ofusing a feed pump for supplying air, but nitrogen or other kind of gasmay be supplied from a high-pressure gas cylinder.

Second Exemplary Embodiment

A method of magnetic transfer of a second exemplary embodiment of thepresent invention will now be described by referring to FIG. 17.

A flow chart of processes of this exemplary embodiment is shown in FIG.17. Each of the processes is same as that of the first exemplaryembodiment. Different points of this exemplary embodiment are that asurface roughness of a master disc for magnetic transfer is measured andthe result of measurement is fed back after magnetic transfer isperformed to a regular magnetic disc.

That is, foreign particles that exist on the master disc are measuredusing a particle counter or the like, which uses a backscattered lightdetection method, in FIG. 17 after the magnetic transfer is made to themagnetic disc. The magnetic transfer is continued by installing a newmagnetic disc, if foreign particle is not observed in this step.

However, an operation of suctioning and forced feeding is repeated byinstalling a dummy disc when a number of foreign particles becomes apredetermined value, i.e. three or more in the case of this exemplaryembodiment, since there will be a problem of head crash as describedpreviously if the number of foreign particles on the surface of themaster disc increases and it reaches a certain number or more whilerepeating the magnetic transfer. This improves the surface by executingthe process of suctioning and forced feeding on the master disc 2 ofwhich a surface is deteriorated, thereby magnetic discs having smoothsurfaces can be manufactured again.

In other words, this exemplary embodiment realizes production ofmagnetic discs having smooth surfaces continuously by maintainingregularly the surface of the master disc 2 during the process ofmagnetic transfer.

The inspection of foreign particles on the master disc 2 is notnecessarily required after the magnetic transfer of every singlemagnetic disc. The measurement of the surface roughness of the masterdisc may be made every after execution of a predetermined number of themagnetic transfers. Or, it may be made after execution of the magnetictransfer processes in number of times slightly shorter than a number, asthis number is stored as needed in a form of data signifying thatforeign particles on the master disc are expected to exceed apredetermined value after so many times of the magnetic transfers areexecuted.

A similar result can also be attained even if foreign particles are notnecessarily measured, if the master disc is maintained by installing adummy disc whenever a predetermined number of magnetic discs areprocessed for the magnetic transfer, because the measurement of foreignparticles on the master disc takes a certain amount of time.

Moreover, a similar effect can be achieved by adopting another method inthat an inspection is carried out on a magnetic disc after the magnetictransfer, and a process of suctioning and forced feeding made on themaster disc 2, if a number of foreign particles found on the magneticdisc after the magnetic transfer exceeds a predetermined value.

The above also applies similarly to the dummy disc 1, that foreignparticles on the master disc 2 can be detected by measuring a surface ofthe dummy disc 1 during the suctioning and forced feeding of the masterdisc 2 with respect to the dummy disc 1.

In other words, the foreign particles, if present between the masterdisc and the dummy disc, lodge in the dummy disc 1 side during thesuctioning, and dimples are produced on the surface of the dummy disc 1,since the dummy disc 1 made of aluminum is lower in hardness than themaster disc 2 made of silicon.

Accordingly, magnetic discs of high quality can be manufactured with themaster disc in a state of smooth surface free from foreign particles, ifthe magnetic transfer is made by detecting small dimples on the surfaceof the dummy disc 1 every after a predetermined number of times thesuctioning and forced feeding are performed, and making the magnetictransfer after replacing the dummy disc 1 with a magnetic disc when suchdimples become not detectable.

In this regard, it is desirable for the surface of the dummy disc to bestrong in adhesion in view of its adhesiveness to foreign particles.

In other words, there is a chance that foreign particles, if presentbetween the master disc and the dummy disc, adhere to the master discside since they do not adhere to the surface of the dummy disc if theadhesiveness of the dummy disc is weak. Moreover, it is possible to makean erroneous judgement, when making a determination for presence orabsence of foreign particles from a condition of the surface of thedummy disc, since it has a smooth surface free from the foreignparticles.

On the other hand, the foreign particles on the master disc can beremoved efficiently if the adhesiveness of the dummy disc is strong,since the foreign particles between the master disc and the dummy discadhere to the dummy disc side. Presence and absence of foreign particlescan also be precisely judged from a condition of the surface of thedummy disc.

Accordingly, it is desirable for the dummy disc to be strong in adhesionto foreign particles, in addition to be low in hardness as compared tothe master disc. In a word, it is desirable for the dummy disc notcoated with lubricant.

FIG. 18 shows a relationship between a number of foreign particles anddefects in a master disc and suctioning/forced feeding, in the cases ofusing a dummy disc coated with lubricant and a dummy disc not coatedwith lubricant.

In FIG. 18, circular dots represent the dummy disc not coated withlubricant (sample D), and square dots represent the dummy disc coatedwith the lubricant on a surface thereof (sample E).

It is obvious, when the sample D and the sample E are compared in FIG.18, that the particles on the master disc can be removed efficiently tonearly zero by repeating close contact and separation between the masterdisc and the dummy disc for several times, in the case of the sample D,although the numbers of foreign particles and defects on the masterdiscs are same at the initial stage. To the contrary, it is clear in thecase of the sample E that the number of foreign particles and defectsdoes not decrease substantially after the 100 cycles of close contactand separation.

In addition, FIGS. 19A and 19B schematically illustrate envelopes ofreproduced signals, when the signals are recorded first in magneticdiscs after magnetic transfer, and the signals are reproducedthereafter.

FIG. 19A shows the envelope taken from the magnetic disc, on whichmagnetic transfer is performed from a master disc after repeatingsuctioning and forced feeding 1000 times on it using a dummy disc coatedwith lubricant. FIG. 19B shows the envelope taken from the magneticdisc, on which magnetic transfer is made from a master disc afterrepeating suctioning and forced feeding 1000 times on it using a dummydisc not coated with lubricant.

As shown in FIG. 19A, there is observed portions marked 50 where signaloutput is reduced in a center portion of the envelope, whereas noreduced portion is seen in the signal of FIG. 19B.

In respect of the fact with FIG. 19A, it is conceivable that the signalhas not been recorded properly due to a spacing loss that has occurredduring the magnetic transfer from the master disc, as a foreign particlehas remained on the master disc even if defect has not been observed onthe surface of the magnetic disc.

To the contrary, it is considered that no spacing loss has occurred inthe signal of FIG. 19B as foreign particles on the master disc have beenremoved completely and the magnetic transfer was performed normally tothe magnetic disc, since the suctioning and forced feeding have beenprocessed on the master disc with the dummy disc not coated withlubricant.

Third Exemplary Embodiment

A method of magnetic transfer of a third exemplary embodiment of thepresent invention will be described next by referring to FIGS. 20A toFIG. 21.

This exemplary embodiment differs from those of the first and the secondexemplary embodiments in a respect that an area of close contact on amaster disc 2 for magnetic transfer during suctioning and forced feedingbetween the master disc 2 and a dummy disc 1 completely includes an areaof the magnetic transfer when the magnetic transfer is made on a regularmagnetic disc 100.

FIGS. 20A and 20B are illustrations schematically depicting relationsbetween the master disc 2 and the dummy disc 1 during the suctioning andforced feeding. In FIG. 20A, foreign particles 62 in an area L areremoved by the suctioning and forced feeding between the master disc 2and the dummy disc 1.

In the next step, when magnetic transfer is made after replacing thedummy disc 1 with a magnetic disc 100, there is a case that an edge ofthe magnetic disc 100 occasionally comes in contact with foreignparticles 62 as shown in FIG. 20B due to a shift in position ofinstallation of the magnetic disc 100, if the dummy disc 1 and themagnetic disc 100 are of the same size.

If this occurs, an output of servo signals transferred to the magneticdisc 100 decreases because of a spacing loss caused by a reduction indegree of contact between the magnetic disc 100 and the master disc 2 invicinity of the foreign particles 62.

This subsequently results in a reading error, and thereby causing adisorder in rotation of the magnetic disc 100.

For this reason, a dummy disc 1 having a size greater than the magneticdisc 100 is adopted in this exemplary embodiment in order to increasethe area L shown in FIG. 20A. Accordingly, this embodiment allows anormal magnetic transfer over an entire surface of the magnetic disc100, and realizes manufacture of the magnetic disc 100 of high qualitywithout causing a reduction in output of the servo signal even if ashift occurs in position of the installation of the magnetic disc 100with respect to the dummy disc 1.

There are often cases of using a magnetic disc 100 taken normally in amid-stage of manufacturing process as a dummy disc 1. Since they areboth equal in size, the dummy disc 1 may intentionally be decenteredduring the suctioning and forced feeding between the dummy disc 1 andthe master disc 2 in order to achieve the effect described above. Inother words, the suctioning and forced feeding can be made over an areathat cover the magnetic disc 100 completely, when a contacting positionof the dummy disc 1 is shifted successively from X, Y, Z, . . . withrespect to the master disc 2 each time the suctioning and forced feedingis made, as shown in FIG. 21.

Fourth Exemplary Embodiment

A method of magnetic transfer of a fourth exemplary embodiment of thepresent invention will be described next by referring to FIGS. 22 to 24.

This exemplary embodiment differs from those of the first through thethird exemplary embodiments in respects that magnetic discs are greaterin hardness than a master disc 2 made of silicon, because glass havinghardness higher than silicon is used as a material of them, and that adummy master disc is adopted.

FIG. 22 shows a flow chart for processes of this exemplary embodiment.Each of the processes is similar to that of the first exemplaryembodiment.

First, a dummy master disc made of silicon is installed in an apparatus,and a regular magnetic disc having a magnetic layer formed thereon isinstalled in the apparatus, in FIG. 22.

Then, a process of suctioning and forced feeding is repeated between thedummy master disc and the magnetic disc in the like manner as the firstexemplary embodiment, and a magnetic transfer is carried out after thedummy master disc is replaced with a regular master disc.

In this process, the magnetic disc does not receive any defect eventhough a defect occurs on the dummy master disc side due to foreignparticles caught between the dummy master disc and the magnetic discwhen they make a close contact with each other, since material of themagnetic disc is glass having hardness greater than silicon. On theother hand, fine foreign particles present on a surface of the magneticdisc are removed by the dummy master disc.

A result of observation on the surface of the magnetic disc in thisexemplary embodiment is shown in FIGS. 23 and 24. FIG. 24 shows acondition of the surface of the magnetic disc in an initial stage beforethe suctioning and forced feeding are made. Table 4 shows a relationbetween depth of defects and number of the defects in this case. It isknown from Table 4 that there are 6 defects having 30 nm or more indepth, and uncountable number of smaller defects in existence in themagnetic disc.

TABLE 3 Depth of 20 nm 30 nm 40 nm 50 nm 60 nm Defects or deeper ordeeper or deeper or deeper or deeper Number of 3 0 0 0 0 defects

TABLE 4 Depth of 20 nm 30 nm 40 nm 50 nm 60 nm Defects or deeper ordeeper or deeper or deeper or deeper Number of 9 6 2 2 1 defects

FIG. 23 shows a condition of the surface of the magnetic disc whenmagnetic transfer is executed using the master disk after one cycle ofsuctioning and forced feeding with the dummy disc is made. Table 3 showsa relation between depth of defects and number of the defects in thiscase. It is known from Table 3 that no defect in depth equal to ordeeper than 30 nm is found, and practically none of the smaller defectsexists, but only an extremely smooth surface.

In this exemplary embodiment, a material having hardness greater thanthe material of the master disc for magnetic transfer is used as thematerial of the magnetic disc. Therefor, it is conceivable that smallbumps and fine foreign particles that exist on the surface of themagnetic disc are removed by a close contact of the dummy master discand the process of suctioning and force-feeding, rather than bytranscription of a shape of dimples and ridges on the surface of themaster disc onto the surface of the magnetic disc.

As has been described, an apparatus for magnetic transfer of thisexemplary embodiment removes the foreign particles by executing theprocess of suctioning and force-feeding by using the dummy master dischaving hardness lower than the magnetic disc to smooth the surface ofthe magnetic disc, and carries out the process of magnetic transfer tothe magnetic disc with the master disc for magnetic transfer.Accordingly, this exemplary embodiment enables the apparatus formagnetic transfer to the magnetic disc having nearly no foreignparticles or anomalous bumps, and to manufacture magnetic discs of highquality with extremely smooth surfaces.

Industrial Applicability

As described above, in a manufacturing method for magneticallytransferring a pattern of magnetic film of a master disc for magnetictransfer into a surface of a magnetic disc according to the presentinvention, a surface of the master disc for magnetic transfer can becleaned, kept smooth and free from burrs by repeating suctioning andforcefully feeding of gas between a dummy disc and the master disc formagnetic transfer prior to the transferring into a regular magneticdisc, thereby realizing manufacture of magnetic discs of high quality.

Furthermore, according to the present invention, foreign particlesadhering on a surface of the master disc for magnetic transfer can beremoved reliably with a measurement of the surface of the master discfor magnetic transfer after completing the magnetic transfer, and byrepeating the suctioning and forced feeding of gas between the dummydisc and the master disc for magnetic transfer when the foreignparticles are detected on the surface of the master disc for magnetictransfer, thereby realizing an apparatus for magnetic transfer of highdurability and the magnetic discs of high quality.

In addition, according to the present invention, fine foreign particlesin existence on the magnetic disc can be removed by using materialgreater in hardness than material of the master disc for magnetictransfer for the magnetic disc, and by repeating the suctioning andforced feeding of gas between a dummy master disc and the regularmagnetic disc, thereby realizing manufacture of the magnetic discs ofhigh quality with extremely smooth surfaces.

What is claimed is:
 1. A method of manufacturing magnetic recordingmedium for magnetic transferring a prestored pattern of data signal froma magnetic film on a surface of a master disc to a surface of anunformatted magnetic disc, said method comprising the steps of: cleaningsaid master disc by contacting with and separating from the magneticfilm surface of said master disc, with and from a dummy disc;overlapping said master disc with said magnetic disc after said step ofcleaning; and magnetizing said magnetic film on said master disc.
 2. Themethod of manufacturing magnetic recording medium for magnetictransferring according to claim 1, further comprising the step ofinspection for detecting a defect in said magnetic disc after themagnetic transfer to said magnetic disc, wherein said step ofoverlapping is performed again after performing said step of cleaningwhen a defect is detected by said step of inspection.
 3. The method ofmanufacturing magnetic recording medium for magnetic transferringaccording to claim 1, wherein said step of cleaning said master disc isexecuted by contacting and separating the surface of said master discwhereon said magnetic film is formed with and from said dummy disc aftera predetermined number of said magnetic discs are magneticallytransferred.
 4. The method of manufacturing magnetic recording mediumfor magnetic transferring according to claim 1, further comprising thestep of repetitively contacting and separating said master disc with andfrom said dummy disc for a predetermined number of times, wherein saidstep of magnetic transferring is performed by contacting said magneticdisc and said master disc after a predetermined number of repetitions.5. The method of manufacturing magnetic recording medium for magnetictransferring according to claim 1, further comprising the step ofinspection for detecting a defect in a surface of a disc, wherein anoperation of contacting and separating said master disc and said dummydisc is repeated for a predetermined number of times before magneticprinting from said master disc to said magnetic disc, when a number ofdefects detected in one of said magnetic disc is equal to or greaterthan the predetermined number of defects detected in said master disc.6. The method of manufacturing magnetic recording medium for magnetictransferring according to claim 1, wherein an operation of contactingand separating said master disc with and from said dummy disc isrepeated for a predetermined number of times after a predeterminednumber of said magnetic discs are magnetically printed.
 7. The method ofmanufacturing magnetic recording medium for magnetic transferringaccording to one of claims 1 to 6, wherein said operation of contactingand separating is made by suctioning gas between said master disc andsaid dummy disc, and by supplying gas between said master disc and saiddummy disc.
 8. The method of manufacturing magnetic recording medium formagnetic transferring according to one of claims 1 to 6, whereinhardness of said master disc is greater than hardness of said magneticdisc and said dummy disc.
 9. The method of manufacturing magneticrecording medium for magnetic transferring according to one of claims 1to 6, wherein hardness of said dummy disc is lower than hardness of saidmagnetic disc.
 10. The method of manufacturing magnetic recording mediumfor magnetic transferring according to one of claims 1 to 6, wherein anarea for contact of said master disc to said dummy disc is equivalent toan area wherein said magnetic transferring is performed from said masterdisc print to said magnetic disc.
 11. The method of manufacturingmagnetic recording medium for magnetic transferring according to one ofclaims 1 to 6, wherein said master disc is cleaned by repeating contactand separation between said master disc and said dummy disc and saiddummy disc is uncoated with lubricant.
 12. The method of manufacturingmagnetic recording medium for magnetic transferring according to one ofclaims 1 to 6, wherein said dummy disc is formed with a plated layer ona surface thereof.
 13. The method of manufacturing magnetic recordingmedium for magnetic transferring according to claim 12, wherein saidplated layer has magnetic property of ferromagnetism.
 14. A method ofmanufacturing magnetic recording medium for magnetic transferring apattern of data signal from a master disc to a magnetic disc as amagnetized pattern of the data signal, by overlapping said master discon a surface of said magnetic disc, and by magnetizing a magnetic filmon said master disc, said master disc having said magnetic film formedthereon in a shape of the pattern corresponding to a predetermined datasignal, said method comprising the steps of: repeating an operation ofcontacting and separating a dummy master disc with and from saidmagnetic disc for a predetermined number of times; and magneticallyprinting by contacting said master disc with said magnetic disc aftersaid step of repeating.
 15. The method of manufacturing magneticrecording medium for magnetic transferring according to claim 14,wherein said operation of contacting and separating is executed bysuctioning gas between said both discs subject to the close contact andseparation, and by supplying gas thereafter.
 16. The method ofmanufacturing magnetic recording medium for magnetic transferringaccording to claim 15, wherein hardness of said dummy master disc islower than hardness of said magnetic disc.